The present invention relates to a power operated sanding machine, and more particularly, a hand-manupulated portable sanding machine which performs orbitary sanding operation with respect to a workpiece.
A sanding machine generally includes a pad for supporting a sanding paper, a pad base connecting with the pad and a power source. According to a conventional sanding machine, a pad base is suspended to a frame through a flexible suspension means so as to minimize vibration to be transmitted to an operator from a workpiece as disclosed in U.S. Pat. No. 4,549,371 commonly assigned. Further, the pad base is generally secured to the suspension means by means of screws. That is, for fixing the pad base to the suspension means, holes formed in the pad base are aligned with holes of the suspension means, and then the screw is inserted into these holes.
In such fixing structure, the suspension means is rotationally distorted due to its flexibility when the screw is threadingly engaged with the holes of the suspension means. In case of the over-distortion, the suspension means may be broken. Further, it would be rather difficult to provide positional alignment between the holes of the pad base and the suspension means, since the pad base covers the holes of the suspension means. Therefore, sufficient assembleability may not be attainable.
Further, according to another conventional sanding machine described in U.S. Pat. No. 3,849,943, the pad is directly bonded to the underside of the pad base by adhesive agent. Therefore, if the replacement of the pad is required, the pad together with the pad base are replaced by a new one. However, the pad base is generally coupled to an eccentric shaft for a fan which shaft is connected to a motor shaft, or the pad base is coupled to a bearing portion of the fan which is connected to the eccentric shaft connected to the motor shaft by a pin. Further, the pad base is also connected, through the screws, to the suspension means suspended from a main frame of the sanding machine. Therefore, in order to remove the pad base from the sanding machine, various mechanical components must be disassembled. Such disassembling work is troublesome and time consuming. Furthermore, various kinds of pad bases are required in accordance with the variations of the pads, which in turn increases overall costs.
According to still another aspect, according to the conventional sanding machine, if the sanding machine is dropped or is mechanically interfered with ambient rigid components, external force is applied to the sander. In this case, since the suspension means is formed of elastic material such as resin or rubber reinforced by a wire, the suspension means is largely bent deformed due to the external impact. If the deformation exceeds an allowable elastic deformation range which is required for ordinary orbitary sanding work, the suspension means may be broken. Therefore, such excessive displacement or distortion of the suspension means must be obviated.
Furthermore, according to a conventional sanding machine, a sanding paper must be provided over the pad. For fixing the sanding paper to the sander, one end of the sanding paper is secured between a paper clamp means and an upper surface of the pad base. However, it would be rather difficult to fix the sanding paper at a proper orientation. If the paper is not suitably secured, the paper may be displaced with respect to the pad, or the paper may be distorted when both ends of the paper is secured to the sander. Therefore, in the conventional sanding machine, sanding paper fixing work is repeatedly carried out so as to correctly position the sanding paper with respect to the pad, which is troublesome and time consuming.